Rankine cycle system

ABSTRACT

A Rankine cycle system having a working medium circulation circuit ( 110 ) that includes an evaporator ( 112 ), an expander ( 113 ), a condenser ( 114 ), and a feed pump ( 115 ) is provided in which a mixture of oil for lubricating the expander ( 113 ) and water, which is a working medium and has become mixed with the oil, is supplied to coalescer type water separating means ( 118 ), thus separating the water from the oil. The oil from which water has been separated in water separating means ( 118 ) is returned to the expander ( 113 ), and the water separated from the oil is returned to the working medium circulation circuit ( 110 ). It is thus unnecessary to replenish the working medium circulation circuit ( 110 ) with water or replenish the expander ( 113 ) with oil.

FIELD OF THE INVENTION

The present invention relates to a Rankine cycle system having anevaporator, an expander, a condenser, and a feed pump provided along aworking medium circulation circuit and, in particular, to a Rankinecycle system provided with means for separating a working medium thathas become mixed with a lubricating medium of the expander, or to aRankine cycle system provided with means for separating the lubricatingmedium of the expander that has become mixed with the working medium.

BACKGROUND ART

When a lubricating medium of an expander has become mixed with a workingmedium circulating around a closed circuit of a Rankine cycle system,the amount of lubricating medium in the expander becomes insufficient,thus degrading the efficiency of the expander or causing seizing.Japanese Utility Model Publication No. 61-8170 discloses a gas/liquidseparator for separating a lubricating medium from a working medium andreturning it to an expander.

There is also known from Japanese Patent Application Laid-open No.63-156508 a so-called coalescer type oil/water separating filter inwhich, by supplying a mixture of oil and water to an ultrafine fiberfilter, oil droplets attached to the fiber become coarser and thusseparate from the water by virtue of the difference in specific gravitybetween the oil and water, or water droplets attached to the fiberbecome coarser and thus separate from the oil by virtue of thedifference in specific gravity between water and the oil.

However, in the Rankine cycle system disclosed in Japanese Utility ModelPublication No. 61-8170, since the mixture of the working medium and thelubricating medium circulates in the closed circuit, there is apossibility that the lubricating medium in the working mediumcirculating in the closed circuit might gasify due to heat, thusaffecting the performance and the durability of the Rankine cyclesystem. Furthermore, since a mixture of liquid-phase working medium,gas-phase working medium, and lubricating medium is supplied from aboiler to the gas/liquid separator and, moreover, the gas/liquidseparator has a structure in which the lubricating medium is separatedby gravity, there is the problem that it is impossible to prevent theliquid-phase working medium from becoming mixed with the lubricatingmedium.

DISCLOSURE OF THE INVENTION

The present invention has been achieved under the above-mentionedcircumstances, and it is an object thereof to provide a Rankine cyclesystem equipped with an expander that is lubricated by a lubricatingmedium, the lubricating medium of the expander being regenerated byreliably separating a working medium that has become mixed with thelubricating medium, or the working medium being regenerated by reliablyseparating the lubricating medium that has become mixed with the workingmedium in the expander.

In order to achieve this object, in accordance with a first aspect ofthe present invention, there is proposed a Rankine cycle system thatincludes a working medium circulation circuit that includes anevaporator that generates a high-temperature, high-pressure gas-phaseworking medium by heating a liquid-phase working medium by means ofwaste heat of a heat engine, an expander that converts the heat andpressure of the gas-phase working medium supplied from the evaporatorinto mechanical energy, a condenser that cools the gas-phase workingmedium whose temperature and pressure have decreased in the expander toturn the working medium back into the liquid-phase working medium, and afeed pump that supplies the liquid-phase working medium discharged fromthe condenser to the evaporator, characterized in that the expander hasa sliding section thereof lubricated by a lubricating medium that isdifferent from the working medium, the Rankine cycle system furtherincludes working medium separating means for separating from thelubricating medium the working medium that has become mixed with thelubricating medium in the expander, and the working medium separatingmeans is provided at a position where the working medium is in aliquid-phase state.

In accordance with this arrangement, when separating the working mediumcontained in the lubricating medium of the expander of the Rankine cyclesystem, the lubricating medium is separated when the working medium isin the liquid-phase state, and it is therefore possible to separate thelubricating medium from the working medium more completely than can bedone in a case in which the liquid-phase working medium and thegas-phase working medium are mixed.

Furthermore, in accordance with a second aspect of the presentinvention, in addition to the first aspect, there is proposed a Rankinecycle system wherein the working medium separating means exhibits afunction of separating the working medium in a predetermined temperaturerange, and the working medium separating means is provided at a positionwhere the lubricating medium is in the predetermined temperature range.

In accordance with this arrangement, since the working medium separatingmeans that exhibits the function of separating the working medium in thepredetermined temperature range is provided at a position where thetemperature of the lubricating medium is in the predeterminedtemperature range, the function of separating the working medium can beexhibited stably while preventing any damage to the working mediumseparating means.

Moreover, in accordance with a third aspect of the present invention, inaddition to the first or second aspect, there is proposed a Rankinecycle system wherein the working medium separating means is formed byconnecting at least two working medium separating devices in line.

In accordance with this arrangement, since the working medium separatingmeans is formed by connecting in line at least two working mediumseparating devices, it is possible to vary the separationcharacteristics of each of the working medium separating devices, andthe separation performance can be improved and the dimensions of theworking medium separating means can be reduced compared with a case inwhich the working medium separating means is formed from one workingmedium separating device.

Furthermore, in accordance with a fourth aspect of the presentinvention, there is proposed a Rankine cycle system that includes aworking medium circulation circuit that includes an evaporator thatgenerates a high-temperature, high-pressure gas-phase working medium byheating a liquid-phase working medium by means of waste heat of a heatengine, an expander that converts the heat and pressure of the gas-phaseworking medium supplied from the evaporator into mechanical energy, acondenser that cools the gas-phase working medium whose temperature andpressure have decreased in the expander to turn the working medium backinto the liquid-phase working medium, and a feed pump that supplies theliquid-phase working medium discharged from the condenser to theevaporator, characterized in that the expander has a sliding sectionthereof lubricated by a lubricating medium that is different from theworking medium, the Rankine cycle system further includes lubricatingmedium separating means for separating from the working medium thelubricating medium that has become mixed with the working medium in theexpander, and the lubricating medium separating means is provided at aposition on the downstream side of the expander where the working mediumis in a liquid-phase state.

In accordance with this arrangement, when separating the lubricatingmedium contained in the working medium of the Rankine cycle system, thelubricating medium is separated when the working medium is in aliquid-phase state, and it is therefore possible to separate thelubricating medium from the working medium more completely than can bedone in a case in which both the liquid-phase working medium and thegas-phase working medium are mixed.

Moreover, in accordance with a fifth aspect of the present invention, inaddition to the fourth aspect, there is proposed a Rankine cycle systemwherein the lubricating medium separating means exhibits a function ofseparating the lubricating medium in a predetermined temperature range,and the lubricating medium separating means is provided at a positionwhere the liquid-phase working medium is in the predeterminedtemperature range.

In accordance with this arrangement, since the lubricating mediumseparating means that exhibits the function of separating thelubricating medium in the predetermined temperature range is provided ata position where the temperature of the liquid-phase working medium isin the predetermined temperature range, the function of separating thelubricating medium can be exhibited stably while preventing any damageto the lubricating medium separating means.

Furthermore, in accordance with a sixth aspect of the present invention,in addition to the fourth or fifth aspect, there is proposed a Rankinecycle system that further includes a gas/liquid separator for separatinga liquid phase portion contained in the working medium discharged fromthe expander into the working medium circulation circuit, theliquid-phase working medium separated by the gas/liquid separator beingsupplied to the lubricating medium separating means.

In accordance with this arrangement, since the liquid phase portioncontained in the working medium discharged from the expander into theworking medium circulation circuit is separated by the gas/liquidseparator and supplied to the lubricating medium separating means, theworking medium that is to be supplied to the lubricating mediumseparating means is reliably converted into the liquid phase, therebyimproving the function of separating the lubricating medium.

Moreover, in accordance with a seventh aspect of the present invention,in addition to the first, second, fourth, or fifth aspect, there isproposed a Rankine cycle system that further includes working mediumpurifying means for removing cations or dissolved gas contained in theworking medium that has been discharged from the expander into theworking medium circulation circuit and that has been turned back intothe liquid phase state.

In accordance with this arrangement, since the working medium purifyingmeans removes cations and dissolved gas contained in the working mediumthat has been discharged from the expander into the working mediumcirculation circuit and that has been turned back into the liquid-phasestate, contamination and corrosion of each section of the working mediumcirculation circuit, through which the working medium circulates, can beprevented more reliably.

Furthermore, in accordance with an eighth aspect of the presentinvention, in addition to the first, second, fourth, or fifth aspect,there is proposed a Rankine cycle system wherein the lubricating mediumfrom which the working medium has been separated by the working mediumseparating means is returned to the expander.

In accordance with this arrangement, since the lubricating medium fromwhich the working medium has been separated by the working mediumseparating means is returned to the expander, it is possible to preventthe working medium from becoming mixed with the lubricating medium anddegrading the lubrication performance and, moreover, it is unnecessaryto replenish the expander with the lubricating medium.

Moreover, in accordance with a ninth aspect of the present invention, inaddition to the first, second, fourth, or fifth aspect, there isproposed a Rankine cycle system wherein the working medium separatedfrom the lubricating medium by the working medium separating means isreturned to the working medium circulation circuit.

In accordance with this arrangement, since the working medium from whichthe lubricating medium has been separated by the working mediumseparating means is returned to the working medium circulation circuit,it is possible to prevent any damage to the working medium circulationcircuit due to the lubricating medium becoming mixed with the workingmedium and, moreover, it is unnecessary to replenish the working mediumcirculation circuit with the working medium.

Furthermore, in accordance with a tenth aspect of the present invention,in addition to the first, second, fourth, or fifth aspect, there isproposed a Rankine cycle system wherein the working medium separatingmeans makes droplets of the working medium contained in the lubricatingmedium become coarse, and the working medium is separated by virtue of adifference in specific gravity between the lubricating medium and theworking medium that has been made into coarse droplets.

In accordance with this arrangement, since the working medium separatingmeans makes the droplets of the working medium become coarse andseparates them from the lubricating medium by virtue of the differencein specific gravity, the working medium can be separated effectivelyfrom the lubricating medium with small pressure loss.

Moreover, in accordance with an eleventh aspect of the presentinvention, in addition to the first, second, fourth, or fifth aspect,there is proposed a Rankine cycle system wherein the working mediumseparating means is of a coalescer type.

In accordance with this arrangement, since the working medium separatingmeans is of the coalescer type, the working medium can be separatedeffectively from the lubricating medium with small pressure loss.

Furthermore, in accordance with a twelfth aspect of the presentinvention, in addition to the eleventh aspect, there is proposed aRankine cycle system wherein the working medium separating meansincludes a filter element formed from hydrophobic fiber.

In accordance with this arrangement, since the filter element of theworking medium separating means is made of the hydrophobic fiber, theability to separate the working medium from the lubricating medium canbe improved.

Moreover, in accordance with a thirteenth aspect of the presentinvention, there is proposed a Rankine cycle system that includes aworking medium circulation circuit that includes an evaporator thatgenerates a high-temperature, high-pressure gas-phase working medium byheating a liquid-phase working medium by means of waste heat of a heatengine, an expander that converts the heat and pressure of the gas-phaseworking medium supplied from the evaporator into mechanical energy, acondenser that cools the gas-phase working medium whose temperature andpressure have decreased in the expander to turn the working medium backinto the liquid-phase working medium, and a feed pump that supplies theliquid-phase working medium discharged from the condenser to theevaporator, characterized in that the expander has a sliding sectionthereof lubricated by a lubricating medium that is different from theworking medium, the Rankine cycle system further includes working mediumseparating means for separating from the lubricating medium the workingmedium that has become mixed with the lubricating medium in theexpander, and the lubricating medium is a hydrophobic oil containing noextreme pressure additive having surface activity.

In accordance with this arrangement, when separating the working mediumcontained in the lubricating medium of the expander by the workingmedium separating means, since the lubricating medium is a hydrophobicoil containing no extreme pressure additive having surface activity, itis possible to prevent any degradation in the lubrication performancedue to emulsification of the lubricating medium and, moreover, theability to separate the working medium and the lubricating medium can beimproved.

Water and steam of an embodiment correspond to the working medium of thepresent invention, an oil of the embodiment corresponds to thelubricating medium of the present invention, an internal combustionengine 111 of the embodiment corresponds to the heat engine of thepresent invention, water separating means 118 of the embodimentcorresponds to the working medium separating means of the presentinvention, an upstream side water separating device 121 and a downstreamside water separating device 122 of the embodiment correspond to theworking medium separating device of the present invention, waterpurifying means 132 of the embodiment corresponds to the working mediumpurifying means of the present invention, and oil separating means 137of the embodiment corresponds to the lubricating medium separating meansof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 to FIG. 25 illustrate one embodiment of the present invention;FIG. 1 is a vertical sectional view of an expander;

FIG. 2 is a sectional view along line 2—2 in FIG. 1;

FIG. 3 is an enlarged view of part 3 in FIG. 1;

FIG. 4 is an enlarged sectional view of part 4 in FIG. 1 (sectional viewalong line 4—4 in FIG. 8);

FIG. 5 is a view from arrowed line 5—5 in FIG. 4;

FIG. 6 is a view from arrowed line 6—6 in FIG. 4;

FIG. 7 is a sectional view along line 7—7 in FIG. 4;

FIG. 8 is a sectional view along line 8—8 in FIG. 4;

FIG. 9 is a sectional view along line 9—9 in FIG. 4;

FIG. 10 is a view from arrowed line 10—10 in FIG. 1;

FIG. 11 is a view from arrowed line 11—11 in FIG. 1;

FIG. 12 is a sectional view along line 12—12 in FIG. 10;

FIG. 13 is a sectional view along line 13—13 in FIG. 11;

FIG. 14 is a sectional view along line 14—14 in FIG. 10;

FIG. 15 is a graph showing torque variations of an output shaft;

FIG. 16 is an explanatory diagram showing the operation of an intakesystem of a high-pressure stage;

FIG. 17 is an explanatory diagram showing the operation of a dischargesystem of the high-pressure stage and an intake system of a low-pressurestage; and

FIG. 18 is an explanatory diagram showing the operation of a dischargesystem of the low-pressure stage;

FIG. 19 is a diagram showing the overall arrangement of the Rankinecycle system;

FIG. 20 is a diagram showing the structure of water separating means;

FIG. 21 is a sectional view along line 21—21 in FIG. 20;

FIG. 22 is a sectional view along line 22—22 in FIG. 20;

FIGS. 23A and 23B are diagrams showing the operation of a coalescer typefilter for separating water;

FIGS. 24A and 24B are diagrams showing the operation of a coalescer typefilter for separating oil; and

FIG. 25 is a diagram showing the structure of oil separating means.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention is explained below with referenceto the attached drawings.

Firstly, an outline of the structure of an expander 113 of a Rankinecycle system is explained with reference to FIG. 1 to FIG. 3.

The expander 113 converts the thermal energy and the pressure energy ofhigh-temperature, high-pressure steam as a working medium intomechanical energy and outputs it. A casing 11 of the expander 113 isformed from a casing main body 12, a front cover 15 fitted via a seal 13into a front opening of the casing main body 12 and joined thereto via aplurality of bolts 14, and a rear cover 18 fitted via a seal 16 onto arear opening of the casing main body 12 and joined thereto via aplurality of bolts 17. An oil pan 19 abuts against a lower opening ofthe casing main body 12 via a seal 20 and is joined thereto via aplurality of bolts 21. Furthermore, a breather chamber dividing wall 23is superimposed on an upper surface of the casing main body 12 via aseal 22 (see FIG. 12), a breather chamber cover 25 is furthersuperimposed on an upper surface of the breather chamber dividing wall23 via a seal 24 (see FIG. 12), and they are together secured to thecasing main body 12 by means of a plurality of bolts 26.

A rotor 27 and an output shaft 28 that can rotate around an axis Lextending in the fore-and-aft direction in the center of the casing 11are united by welding. A rear part of the rotor 27 is rotatablysupported in the casing main body 12 via an angular ball bearing 29 anda seal 30, and a front part of the output shaft 28 is rotatablysupported in the front cover 15 via an angular ball bearing 31 and aseal 32. A swash plate holder 36 is fitted via two seals 33 and 34 and aknock pin 35 in a rear face of the front cover 15 and fixed thereto viaa plurality of bolts 37, and a swash plate 39 is rotatably supported inthe swash plate holder 36 via an angular ball bearing 38. The rotationalaxis of the swash plate 39 is inclined relative to the axis L of therotor 27 and the output shaft 28, and the angle of inclination is fixed.

Seven sleeves 41 formed from members that are separate from the rotor 27are arranged within the rotor 27 so as to surround the axis L at equalintervals in the circumferential direction. High-pressure pistons 43 areslidably fitted in high-pressure cylinders 42 formed at innerperipheries of the sleeves 41, which are supported by sleeve supportbores 27 a of the rotor 27. Hemispherical parts of the high-pressurepistons 43 projecting forward from forward end openings of thehigh-pressure cylinders 42 abut against seven dimples 39 a recessed in arear surface of the swash plate 39. Heat resistant metal seals 44 arefitted between the rear ends of the sleeves 41 and the sleeve supportbores 27 a of the rotor 27, and a single set plate 45 retaining thefront ends of the sleeves 41 in this state is fixed to a front surfaceof the rotor 27 by means of a plurality of bolts 46. The sleeve supportbores 27 a have a slightly larger diameter in the vicinity of theirbases, thus forming a gap α (see FIG. 3) between themselves and theouter peripheries of the sleeves 41.

The high-pressure pistons 43 include pressure rings 47 and oil rings 48for sealing the surfaces that slide against the high-pressure cylinders42, and the sliding range of the pressure rings 47 and the sliding rangeof the oil rings 48 are set so as not to overlap each other. Taperedopenings 45 a widening toward the front are formed in the set plate 45in order to make the pressure rings 47 and the oil rings 48 engagesmoothly with the high-pressure cylinders 42 when the high-pressurepistons 43 are inserted into the high-pressure cylinders 42.

As hereinbefore described, since the sliding range of the pressure rings47 and the sliding range of the oil rings 48 are set so as not tooverlap each other, a lubricating medium oil attached to the inner wallsof the high-pressure cylinders 42 against which the oil rings 48 slidewill not be taken into high-pressure operating chambers 82 due tosliding of the pressure rings 47, thereby reliably preventing the oilfrom contaminating the steam. In particular, the high-pressure pistons43 have a slightly smaller diameter part between the pressure rings 47and the oil rings 48 (see FIG. 3), thereby effectively preventing theoil attached to the sliding surfaces of the oil rings 48 from moving tothe sliding surfaces of the pressure rings 47.

Since the high-pressure cylinders 42 are formed by fitting the sevensleeves 41 in the sleeve support bores 27 a of the rotor 27, a materialhaving excellent thermal conductivity, heat resistance, abrasionresistance, strength, etc. can be selected for the sleeves 41. This notonly improves the performance and the reliability, but also machiningbecomes easy compared with a case in which the high-pressure cylinders42 are directly machined in the rotor 27, and the machining precisionalso increases. When any one of the sleeves 41 is worn or damaged, it ispossible to replace only the faulty sleeve 41, without replacing theentire rotor 27, and this is economical.

Furthermore, since the gap α is formed between the outer periphery ofthe sleeves 41 and the rotor 27 by slightly enlarging the diameter ofthe sleeve support bores 27 a in the vicinity of the base, even when therotor 27 is thermally deformed by the high-temperature, high-pressuresteam supplied to the high-pressure operating chambers 82, this isprevented from affecting the sleeves 41, thereby preventing thehigh-pressure cylinders 42 from distorting.

The seven high-pressure cylinders 42 and the seven high-pressure pistons43 fitted therein form a first axial piston cylinder group 49.

Seven low-pressure cylinders 50 are arranged at circumferentially equalintervals on the outer peripheral part of the rotor 27 so as to surroundthe axis L and the radially outer side of the high-pressure cylinders42. These low-pressure cylinders 50 have a larger diameter than that ofthe high-pressure cylinders 42, and the pitch at which the low-pressurecylinders 50 are arranged in the circumferential direction is displacedby half a pitch relative to the pitch at which the high-pressurecylinders 42 are arranged in the circumferential direction. This makesit possible for the high-pressure cylinders 42 to be arranged in spacesformed between adjacent low-pressure cylinders 50, thus utilizing thespaces effectively and contributing to a reduction in the diameter ofthe rotor 27.

The seven low-pressure cylinders 50 have low-pressure pistons 51slidably fitted thereinto, and these low-pressure pistons 51 areconnected to the swash plate 39 via links 52. That is, spherical parts52 a at the front end of the links 52 are swingably supported inspherical bearings 54 fixed to the swash plate 39 via nuts 53, andspherical parts 52 b at the rear end of the links 52 are swingablysupported in spherical bearings 56 fixed to the low-pressure pistons 51by clips 55. A pressure ring 78 and an oil ring 79 are fitted around theouter periphery of each of the low-pressure pistons 51 in the vicinityof the top surface thereof so as to adjoin each other. Since the slidingranges of the pressure ring 78 and the oil ring 79 overlap each other,an oil film is formed on the sliding surface of the pressure ring 78,thus enhancing the sealing characteristics and the lubrication.

The seven low-pressure cylinders 50 and the seven low-pressure pistons41 fitted therein form a second axial piston cylinder group 57.

An oil used in a reciprocating engine, etc. contains a surfactant and anextreme pressure agent. Representative examples of the extreme pressureagent include molybdenum compounds represented by molybdenum sulfides(e.g., molybdenum disulfide, etc.). When the oil (hydrophilic oil) towhich an extreme pressure agent has been added is strongly agitated,water is surrounded by the extreme pressure agent and the surfactant,which have hydrophilic groups, and not only is the function as alubricating oil degraded, but also it becomes difficult to carry outseparation of water since the emulsified mixture is stabilized. Becauseof this, in this embodiment a hydrophobic oil containing no hydrophilicadditive is used as the lubricating medium of the expander 113.

As hereinbefore described, since the front ends of the high-pressurepistons 43 of the first axial piston cylinder group 49 are made in theform of hemispheres and are made to abut against the dimples 39 a formedin the swash plate 39, it is unnecessary to connect the high-pressurepistons 43 to the swash plate 39 mechanically, thus reducing the numberof parts and improving the ease of assembly. On the other hand, thelow-pressure pistons 51 of the second axial piston cylinder group 57 areconnected to the swash plate 39 via the links 52 and their front andrear spherical bearings 54 and 56, and even when the temperature and thepressure of medium-temperature, medium-pressure steam supplied to thesecond axial piston cylinder group 57 become insufficient and thepressure of low-pressure operating chambers 84 becomes negative, thereis no possibility of the low-pressure pistons 51 becoming detached fromthe swash plate 39 and causing knocking or damage.

Furthermore, when the swash plate 39 is secured to the front cover 15via the bolts 37, changing the phase at which the swash plate 39 issecured around the axis L enables the timing of supply and discharge ofthe steam to and from the first axial piston cylinder group 49 and thesecond axial piston cylinder group 57 to be shifted, thereby alteringthe output characteristics of the expander 113.

Moreover, since the rotor 27 and the output shaft 28, which are united,are supported respectively by the angular ball bearing 29 provided onthe casing main body 12 and the angular ball bearing 31 provided on thefront cover 15, by adjusting the thickness of a shim 58 disposed betweenthe casing main body 12 and the angular ball bearing 29 and thethickness of a shim 59 disposed between the front cover 15 and theangular ball bearing 31, the longitudinal position of the rotor 27 alongthe axis L can be adjusted. By adjusting the position of the rotor 27 inthe axis L direction, the relative positional relationship in the axis Ldirection between the high-pressure and low-pressure pistons 43 and 51guided by the swash plate 39, and the high-pressure and low-pressurecylinders 42 and 50 provided in the rotor 27 can be changed, therebyadjusting the expansion ratio of the steam in the high-pressure andlow-pressure operating chambers 82 and 84.

If the swash plate holder 36 supporting the swash plate 39 were formedintegrally with the front cover 15, it would be difficult to secure aspace for attaching and detaching the angular ball bearing 31 or theshim 59 to and from the front cover 15, but since the swash plate holder36 is made detachable from the front cover 15, the above-mentionedproblem can be eliminated. Moreover, if the swash plate holder 36 wereintegral with the front cover 15, during assembly and disassembly of theexpander 113 it would be necessary to carry out cumbersome operations ofconnecting and disconnecting the seven links 52, which are in a confinedspace within the casing 11, to and from the swash plate 39 pre-assembledto the front cover 15, but since the swash plate holder 36 is madedetachable from the front cover 15, it becomes possible to form asub-assembly by assembling the swash plate 39 and the swash plate holder36 to the rotor 27 in advance, thereby greatly improving the ease ofassembly.

Systems for supply and discharge of steam to and from the first axialpiston cylinder group 49 and the second axial piston cylinder group 57are now explained with reference to FIG. 4 to FIG. 9.

As shown in FIG. 4, a rotary valve 61 is housed in a circularcross-section recess 27 b opening on the rear end surface of the rotor27 and a circular cross-section recess 18 a opening on a front surfaceof the rear cover 18. The rotary valve 61, which is disposed along theaxis L, includes a rotary valve main body 62, a stationary valve plate63, and a movable valve plate 64. The movable valve plate 64 is fixed tothe rotor 27 via a knock pin 66 and a bolt 67 a in a state in which itis fitted to the base of the recess 27 b of the rotor 27 via a gasket65. The stationary valve plate 63, which abuts against the movable valveplate 64 via a flat sliding surface 68, is joined via a knock pin 69 anda bolt 67 b to the rotary valve main body 62 so that there is norelative rotation therebetween. When the rotor 27 rotates, the movablevalve plate 64 and the stationary valve plate 63 therefore rotaterelative to each other on the sliding surface 68 in a state in whichthey are in intimate contact with each other. The stationary valve plate63 and the movable valve plate 64 are made of a material havingexcellent durability, such as a super hard alloy or a ceramic, and thesliding surface 68 can be provided with or coated with a member havingheat resistance, lubricating properties, corrosion resistance, orabrasion resistance.

The rotary valve main body 62 is a stepped cylindrical member having alarge diameter part 62 a, a medium diameter part 62 b, and a smalldiameter part 62 c; an annular sliding member 70 fitted around the outerperiphery of the large diameter part 62 a is slidably fitted in therecess 27 b of the rotor 27 via a cylindrical sliding surface 71, andthe medium diameter part 62 b and the small diameter part 62 c arefitted in the recess 18 a of the rear cover 18 via seals 72 and 73. Thesliding member 70 is made of a material having excellent durability,such as a super hard alloy or a ceramic. A knock pin 74 implanted in theouter periphery of the rotary valve main body 62 engages with a longhole 18 b formed in the recess 18 a of the rear cover 18 in the axis Ldirection, and the rotary valve main body 62 is therefore supported sothat it can move in the axis L direction but cannot rotate relative tothe rear cover 18.

A plurality of (for example, seven) preload springs 75 are supported inthe rear cover 18 so as to surround the axis L, and the rotary valvemain body 62, which has a step 62 d between the medium diameter part 62b and the small diameter part 62 c pressed by these preload springs 75,is biased forward so as to make the sliding surface 68 of the stationaryvalve plate 63 and the movable valve plate 64 come into intimate contactwith each other. A pressure chamber 76 is defined between the bottom ofthe recess 18 a of the rear cover 18 and the rear end surface of thesmall diameter part 62 c of the rotary valve main body 62, and a steamsupply pipe 77 connected so as to run though the rear cover 18communicates with the pressure chamber 76. The rotary valve main body 62is therefore biased forward by the steam pressure acting on the pressurechamber 76 in addition to the resilient force of the preload springs 75.

A high-pressure stage steam intake route for supplying high-temperature,high-pressure steam to the first axial piston cylinder group 49 is shownin FIG. 16 by a mesh pattern. As is clear from FIG. 16 together withFIG. 5 to FIG. 9, a first steam passage P1 having its upstream endcommunicating with the pressure chamber 76, to which thehigh-temperature, high-pressure steam is supplied from the steam supplypipe 77, runs through the rotary valve main body 62, opens on thesurface at which the rotary valve main body 62 is joined to thestationary valve plate 63, and communicates with a second steam passageP2 running through the stationary valve plate 63. In order to preventthe steam from leaking past the surface at which the rotary valve mainbody 62 and the stationary valve plate 63 are joined, the joiningsurface is equipped with a seal 81 (see FIG. 7 and FIG. 16), which sealsthe outer periphery of a connecting part between the first and secondsteam passages P1 and P2.

Seven third steam passages P3 (see FIG. 5) and seven fourth steampassages P4 are formed respectively in the movable valve plate 64 andthe rotor 27 at circumferentially equal intervals, and the downstreamends of the fourth steam passages P4 communicate with the sevenhigh-pressure operating chambers 82 defined between the high-pressurecylinders 42 and the high-pressure pistons 43 of the first axial pistoncylinder group 49. As is clear from FIG. 6, an opening of the secondsteam passage P2 formed in the stationary valve plate 63 does not openevenly to the front and rear of the top dead center (TDC) of thehigh-pressure pistons 43, but opens displaced slightly forward in thedirection of rotation of the rotor 27, which is shown by the arrow R.This enables as long an expansion period as possible, that is, asufficient expansion ratio, to be maintained, negative work, which wouldbe generated if the opening were set evenly to the front and rear of theTDC, to be minimized and, moreover, the expanded steam remaining in thehigh-pressure operating chambers 82 to be reduced, thus providingsufficient output (efficiency).

A high-pressure stage steam discharge route and a low-pressure stagesteam intake route for discharging medium-temperature, medium-pressuresteam from the first axial piston cylinder group 49 and supplying it tothe second axial piston cylinder group 57 are shown in FIG. 17 by a meshpattern. As is clear from FIG. 17 together with FIG. 5 to FIG. 8, anarc-shaped fifth steam passage P5 (see FIG. 6) opens on a front surfaceof the stationary valve plate 63, and this fifth steam passage P5communicates with a circular sixth steam passage P6 (see FIG. 7) openingon a rear surface of the stationary valve plate 63. The fifth steampassage P5 opens from a position displaced slightly forward in thedirection of rotation of the rotor 27, which is shown by the arrow R,relative to the bottom dead center (BDC) of the high-pressure pistons 43to a position displaced slightly backward in the rotational directionrelative to the TDC. This enables the third steam passages P3 of themovable valve plate 64 to communicate with the fifth steam passage P5 ofthe stationary valve plate 63 over an angular range that starts from theBDC and does not overlap the second steam passage P2 (preferably,immediately before overlapping the second steam passage P2), and in thisrange the steam is discharged from the third steam passages P3 to thefifth steam passage P5.

Formed in the rotary valve main body 62 are a seventh steam passage P7extending in the axis L direction and an eighth steam passage P8extending in a substantially radial direction. The upstream end of theseventh steam passage P7 communicates with the downstream end of thesixth steam passage P6. The downstream end of the seventh steam passageP7 communicates with a tenth steam passage P10 running radially throughthe sliding member 70 via a ninth steam passage P9 within a couplingmember 83 disposed so as to bridge between the rotary valve main body 62and the sliding member 70. The tenth steam passage P10 communicates withthe seven low-pressure operating chambers 84 defined between thelow-pressure cylinders 50 and the low-pressure pistons 41 of the secondaxial piston cylinder group 57 via seven eleventh steam passages P11formed radially in the rotor 27.

In order to prevent the steam from leaking past the joining surfaces ofthe rotary valve main body 62 and the stationary valve plate 63, theouter periphery of a part where the sixth and seventh steam passages P6and P7 are connected is sealed by equipping the joining surfaces with aseal 85 (see FIG. 7 and FIG. 17). Two seals 86 and 87 are disposedbetween the inner periphery of the sliding member 70 and the rotaryvalve main body 62, and a seal 88 is disposed between the outerperiphery of the coupling member 83 and the sliding member 70.

A steam discharge route for discharging low-temperature, low-pressuresteam from the second axial piston cylinder group 57 is shown in FIG. 18by a mesh pattern. As is clear from reference to FIG. 18 together withFIG. 8 and FIG. 9, an arc-shaped sixteenth steam passage P16 that cancommunicate with the seven eleventh steam passages P11 formed in therotor 27 is cut out in the sliding surface 71 of the sliding member 70.This sixteenth steam passage P16 communicates with a seventeenth steampassage P17 that is cut out in an arc-shape in the outer periphery ofthe rotary valve main body 62. The sixteenth steam passage P16 opensfrom a position displaced slightly forward in the direction of rotationof the rotor 27, which is shown by the arrow R, relative to the BDC ofthe low-pressure pistons 51 to a position displaced slightly backward inthe direction of rotation of the rotor 27 relative to the TDC. Thisallows the eleventh steam passages P11 of the rotor 27 to communicatewith the sixteenth steam passage P16 of the sliding member 70 over anangular range that starts from the BDC and does not overlap the tenthsteam passage P10 (preferably, immediately before overlapping the tenthsteam passage P10), and in this range the steam is discharged from theeleventh steam passages P11 to the sixteenth steam passage P16.

The seventeenth steam passage P17 further communicates with a steamdischarge chamber 90 formed between the rotary valve main body 62 andthe rear cover 18 via an eighteenth steam passage P18 to a twentiethsteam passage P20 formed within the rotary valve main body 62 and acutout 18 d of the rear cover 18, and this steam discharge chamber 90communicates with a steam discharge hole 18 c formed in the rear cover18.

As hereinbefore described, since the supply and discharge of the steamto and from the first axial piston cylinder group 49 and the supply anddischarge of the steam to and from the second axial piston cylindergroup 57 are controlled by the common rotary valve 61, in comparisonwith a case in which separate rotary valves are used for each, thedimensions of the expander 113 can be reduced. Moreover, since a valvefor supplying the high-temperature, high-pressure steam to the firstaxial piston cylinder group 49 is formed on the flat sliding surface 68on the front end of the stationary valve plate 63, which is integralwith the rotary valve main body 62, it is possible to preventeffectively the high-temperature, high-pressure steam from leaking. Thisis because the flat sliding surface 68 can be machined easily with highprecision, and control of clearance is easier than for a cylindricalsliding surface.

In particular, since the plurality of preload springs 75 apply a presetload to the rotary valve main body 62 and bias it forward in the axis Ldirection, and the high-temperature, high-pressure steam supplied fromthe steam supply pipe 77 to the pressure chamber 76 biases the rotaryvalve main body 62 forward in the axis L direction, a surface pressureis generated on the sliding surface 68 between the stationary valveplate 63 and the movable valve plate 64 in response to the pressure ofthe high-temperature, high-pressure steam, and it is thus possible toprevent yet more effectively the steam from leaking past the slidingsurface 68.

Although a valve for supplying the medium-temperature, medium-pressuresteam to the second axial piston cylinder group 57 is formed on thecylindrical sliding surface 71 on the outer periphery of the rotaryvalve main body 62, since the pressure of the medium-temperature,medium-pressure steam passing through the valve is lower than thepressure of the high-temperature, high-pressure steam, leakage of thesteam can be suppressed to a practically acceptable level by maintaininga predetermined clearance even without generating a surface pressure onthe sliding surface 71.

Furthermore, since the first steam passage P1 through which thehigh-temperature, high-pressure steam passes, the seventh steam passageP7 and the eighth steam passage P8 through which the medium-temperature,medium-pressure steam passes, and the seventeenth steam passage P17 tothe twentieth steam passage P20 through which the low-temperature,low-pressure steam passes are collectively formed within the rotaryvalve main body 62, not only can the steam temperature be prevented fromdropping, but also the parts (for example, the seal 81) sealing thehigh-temperature, high-pressure steam can be cooled by thelow-temperature, low-pressure steam, thus improving the durability.

Moreover, since the rotary valve 61 can be attached to and detached fromthe casing main body 12 merely by removing the rear cover 18 from thecasing main body 12, the ease of maintenance operations such as repair,cleaning, and replacement can be greatly improved. Furthermore, althoughthe temperature of the rotary valve 61 through which thehigh-temperature, high-pressure steam passes becomes high, since theswash plate 39 and the output shaft 28, where lubrication by oil isrequired, are disposed on the opposite side to the rotary valve 61relative to the rotor 27, the oil is prevented from being heated by theheat of the rotary valve 61 when it is at high temperature, which woulddegrade the performance in lubricating the swash plate 39 and the outputshaft 28. Moreover, the oil can exhibit a function of cooling the rotaryvalve 61, thus preventing overheating.

As is clear from FIG. 1, the oil that is stored in the oil pan 19 isreturned to the expander 113 via an oil passage 91, an oil pump 92driven by the output shaft 28, and an oil reservoir 89 formed within theoutput shaft 28, and during this process water contained in the oil isseparated. The details thereof will be explained later.

The structure of a breather is now explained by reference to FIG. 10 toFIG. 14.

A lower breather chamber 101 defined between an upper wall 12 a of thecasing main body 12 and the breather chamber dividing wall 23communicates with a lubrication chamber 102 within the casing 11 via athrough hole 12 b formed in the upper wall 12 a of the casing main body12. Oil is stored in the oil pan 19 provided in a bottom part of thelubrication chamber 102, and the oil level is slightly higher than thelower end of the rotor 27 (see FIG. 1). Provided within the lowerbreather chamber 101 so as to project upward are three dividing walls 12c to 12 e having their upper ends in contact with a lower surface of thebreather chamber dividing wall 23. The through hole 12 b opens at oneend of a labyrinth formed by these dividing walls 12 c to 12 e, and fouroil return holes 12 f running through the upper wall 12 a are formedpartway along the route to the other end of the labyrinth. The oilreturn holes 12 f are formed at the lowest position of the lowerbreather chamber 101 (see FIG. 14), and the oil condensed within thelower breather chamber 101 can therefore be reliably returned to thelubrication chamber 102.

An upper breather chamber 103 is defined between the breather chamberdividing wall 23 and the breather chamber cover 25, and this upperbreather chamber 103 communicates with the lower breather chamber 101via four through holes 23 a and 23 b running through the breatherchamber dividing wall 23 and projecting chimney-like within the upperbreather chamber 103. A recess 12 g is formed in the upper wall 12 a ofthe casing main body 12 at a position below a condensed water returnhole 23 c running through the breather chamber dividing wall 23, and theperiphery of the recess 12 g is sealed by a seal 104.

One end of a first breather passage B1 formed in the breather chamberdividing wall 23 opens at mid height in the upper breather chamber 103.The other end of the first breather passage B1 communicates with thesteam discharge chamber 90 via a second breather passage B2 formed inthe casing main body 12 and a third breather passage B3 formed in therear cover 18. Furthermore, the recess 12 g, which is formed in theupper wall 12 a, communicates with the steam discharge chamber 90 via afourth breather passage B4 formed in the casing main body 12 and thethird breather passage B3. The outer periphery of a part providingcommunication between the first breather passage B1 and the secondbreather passage B2 is sealed by a seal 105.

As shown in FIG. 2, a coupling 106 communicating with the lower breatherchamber 101 and a coupling 107 communicating with the oil pan 19 areconnected together by a transparent oil level gauge 108, and the oillevel within the lubrication chamber 102 can be checked from the outsideby the oil level of this oil level gauge 108. That is, the lubricationchamber 102 has a sealed structure, it is difficult to insert an oillevel gauge from the outside from the viewpoint of maintaining sealingcharacteristics, and the structure will inevitably become complicated.However, this oil level gauge 108 enables the oil level to be checkedeasily from the outside while maintaining the lubrication chamber 102 ina sealed state.

The operation of the expander 113 having the above-mentioned arrangementis now explained.

As shown in FIG. 16, high-temperature, high-pressure steam generated byheating water in an evaporator is supplied to the pressure chamber 76 ofthe expander 113 via the steam supply pipe 77, and reaches the slidingsurface 68 with the movable valve plate 64 via the first steam passageP1 formed in the rotary valve main body 62 of the rotary valve 61 andthe second steam passage P2 formed in the stationary valve plate 63integral with the rotary valve main body 62. The second steam passage P2opening on the sliding surface 68 communicates momentarily with thethird steam passage P3 formed in the movable valve plate 64 rotatingintegrally with the rotor 27, and the high-temperature, high-pressuresteam is supplied, via the fourth steam passage P4 formed in the rotor27, from the third steam passage P3 to, among the seven high-pressureoperating chambers 82 of the first axial piston cylinder group 49, thehigh-pressure operating chamber 82 that is present at the top deadcenter.

Even after the communication between the second steam passage P2 and thethird steam passage P3 has been blocked due to rotation of the rotor 27,the high-temperature, high-pressure steam expands within thehigh-pressure operating chamber 82 and causes the high-pressure piston43 fitted in the high-pressure cylinder 42 of the sleeve 41 to be pushedforward from top dead center toward bottom dead center, and the frontend of the high-pressure piston 43 presses against the dimple 39 a ofthe swash plate 39. As a result, the reaction force that thehigh-pressure pistons 43 receive from the swash plate 39 gives arotational torque to the rotor 27. For each one seventh of a revolutionof the rotor 27, the high-temperature, high-pressure steam is suppliedinto a fresh high-pressure operating chamber 82, thus continuouslyrotating the rotor 27.

As shown in FIG. 17, while the high-pressure piston 43, which hasreached bottom dead center, moves back toward top dead centeraccompanying rotation of the rotor 27, the medium-temperature,medium-pressure steam pushed out of the high-pressure operating chamber82 is supplied to the eleventh steam passage P11 communicating with thelow-pressure operating chamber 84 that, among the second axial pistoncylinder group 57, has reached top dead center accompanying rotation ofthe rotor 27, via the fourth steam passage P4 of the rotor 27, the thirdsteam passage P3 of the movable valve plate 64, the sliding surface 68,the fifth steam passage P5 and the sixth steam passage P6 of thestationary valve plate 63, the seventh steam passage P7 to the tenthsteam passage P10 of the rotary valve main body 62, and the slidingsurface 71. Since the medium-temperature, medium-pressure steam suppliedto the low-pressure operating chamber 84 expands within the low-pressureoperating chambers 84 even after the communication between the tenthsteam passage P10 and the eleventh steam passage P11 is blocked, thelow-pressure piston 51 fitted in the low-pressure cylinder 50 is pushedforward from top dead center toward bottom dead center, and the link 52connected to the low-pressure piston 51 presses against the swash plate39. As a result, the pressure force of the low-pressure piston 51 isconverted into a rotational force of the swash plate 39 via the link 52,and this rotational force transmits a rotational torque from thehigh-pressure piston 43 to the rotor 27 via the dimple 39 a of the swashplate 39. That is, the rotational torque is transmitted to the rotor 27,which rotates synchronously with the swash plate 39. In order to preventthe low-pressure piston 51 from becoming detached from the swash plate39 when a negative pressure is generated during the expansion stroke,the link 52 carries out a function of maintaining a connection betweenthe low-pressure piston 51 and the swash plate 39, and it is arrangedthat the rotational torque due to the expansion is transmitted from thehigh-pressure piston 43 to the rotor 27 rotating synchronously with theswash plate 39 via the dimples 39 a of the swash plate 39 as describedabove. For each one seventh of a revolution of the rotor 27, themedium-temperature, medium-pressure steam is supplied into a freshlow-pressure operating chamber 84, thus continuously rotating the rotor27.

As shown in FIG. 18, while the low-pressure piston 51, which has reachedbottom dead center, moves back toward top dead center accompanyingrotation of the rotor 27, the low-temperature, low-pressure steam pushedout of the low-pressure operating chamber 84 is discharged into thesteam discharge chamber 90 via the eleventh steam passage P11 of therotor 27, the sliding surface 71, the sixteenth steam passage P16 of thesliding member 70, and the seventeenth steam passage P17 to thetwentieth steam passage P20 of the rotary valve main body 62, and issupplied therefrom into a condenser via the steam discharge hole 18 c.

When the expander 113 operates as described above, since the sevenhigh-pressure pistons 43 of the first axial piston cylinder group 49 andthe seven low-pressure pistons 51 of the second axial piston cylindergroup 57 are connected to the common swash plate 39, the outputs of thefirst and second axial piston cylinder groups 49 and 57 can be combinedto drive the output shaft 28, thereby achieving a high output whilereducing the size of the expander 113. During this process, since theseven high-pressure pistons 43 of the first axial piston cylinder group49 and the seven high-pressure pistons 51 of the second axial pistoncylinder group 57 are displaced by half a pitch in the circumferentialdirection, as shown in FIG. 15, pulsations in the output torque of thefirst axial piston cylinder group 49 and pulsations in the output torqueof the second axial piston cylinder group 57 balance each other out,thus making the output torque of the output shaft 28 flat.

Furthermore, although axial type rotary fluid machinescharacteristically have a higher space efficiency than radial typerotary fluid machines, by arranging two stages in the radial directionthe space efficiency can be further enhanced. In particular, since theaxial piston cylinders of the first group 49, which are required to haveonly a small diameter because they are operated by high-pressure steamhaving a small volume, are arranged on the radially inner side, and theaxial piston cylinders of the second group 57, which are required tohave a large diameter because they are operated by low-pressure steamhaving a large volume, are arranged on the radially outer side, thespace can be utilized effectively, thus making the expander 113 stillsmaller. Moreover, since the cylinders 42 and 50 and the pistons 43 and51 that are used have circular cross sections, which enables machiningto be carried out with high precision, the amount of steam leakage canbe reduced in comparison with a case in which vanes are used, and a yethigher output can thus be anticipated.

Furthermore, since the first axial piston cylinder group 49 operated byhigh-temperature steam is arranged on the radially inner side, and thesecond axial piston cylinder group 57 operated by low-temperature steamis arranged on the radially outer side, the difference in temperaturebetween the second axial piston cylinder group 57 and the outside of thecasing 11 can be minimized, the amount of heat released outside thecasing 11 can be minimized, and the efficiency of the expander 113 canbe enhanced. Moreover, since the heat escaping from the high-temperaturefirst axial piston cylinder group 49 on the radially inner side can berecovered by the low-temperature second axial piston cylinder group 57on the radially outer side, the efficiency of the expander 113 can befurther enhanced.

Moreover, when viewed from an angle perpendicular to the axis L, sincethe rear end of the first axial piston cylinder group 49 is positionedforward relative to the rear end of the second axial piston cylindergroup 57, heat escaping rearward in the axis L direction from the firstaxial piston cylinder group 49 can be recovered by the second axialpiston cylinder group 57, and the efficiency of the expander 113 can beyet further enhanced. Furthermore, since the sliding surface 68 on thehigh-pressure side is present deeper within the recess 27 b of the rotor27 than the sliding surface 71 on the low-pressure side, the differencein pressure between the outside of the casing 11 and the sliding surface71 on the low-pressure side can be minimized, the amount of steamleaking past the sliding surface 71 on the low-pressure side can bereduced and, moreover, the pressure of steam leaking past the slidingsurface 68 on the high-pressure side can be recovered by the slidingsurface 71 on the low-pressure side and utilized effectively.

During operation of the expander 113, the oil accumulated in the oil pan19 is stirred and splashed by the rotor 27 rotating within thelubrication chamber 102 of the casing 11, thereby lubricating slidingsections between the high-pressure cylinders 42 and the high-pressurepistons 43, sliding sections between the low-pressure cylinders 50 andthe low-pressure pistons 51, the angular ball bearing 31 supporting theoutput shaft 28, the angular ball bearing 29 supporting the rotor 27,the angular ball bearing 38 supporting the swash plate 39, slidingsections between the high-pressure pistons 43 and the swash plate 39,the spherical bearings 54 and 56 at opposite ends of the links 52, etc.

The interior of the lubrication chamber 102 is filled with oil mistgenerated by splashing due to stirring of the oil and oil vaporgenerated by vaporization due to heating by a high-temperature sectionof the rotor 27, and this is mixed with steam leaking into thelubrication chamber 102 from the high-pressure operating chambers 82 andlow-pressure operating chambers 84. When the pressure of the lubricationchamber 102 becomes higher than the pressure of the steam dischargechamber 90 due to the leakage of steam, the mixture of oil content andsteam flows through the through hole 12 b formed in the upper wall 12 aof the casing main body 12 into the lower breather chamber 101. Theinterior of the lower breather chamber 101 has a labyrinth structure dueto the dividing walls 12 c to 12 e; the oil that condenses while passingtherethrough drops through the four oil return holes 12 f formed in theupper wall 12 a of the casing main body 12, and is returned to thelubrication chamber 102.

The steam from which the oil content has been removed passes through thefour through holes 23 a and 23 b of the breather chamber dividing wall23, flows into the upper breather chamber 103, and condenses by losingits heat to the outside air via the breather chamber cover 25, whichdefines an upper wall of the upper breather chamber 103. Water that hascondensed within the upper breather chamber 103 passes through thecondensed water return hole 23 c formed in the breather chamber dividingwall 23 and drops into the recess 12 g without flowing into the fourthrough holes 23 a, 23 b projecting chimney-like within the upperbreather chamber 103, and is discharged therefrom into the steamdischarge chamber 90 via the fourth breather passage B4 and the thirdbreather passage B3. Here, the amount of condensed water returned intothe steam discharge chamber 90 corresponds to the amount of steam thathas leaked from the high-pressure operating chambers 82 and thelow-pressure operating chambers 84 into the lubrication chamber 102.Furthermore, since the steam discharge chamber 90 and the upper breatherchamber 103 always communicate with each other via the first steampassage B1 to the third steam passage B3, which function as pressureequilibration passages, pressure equilibrium between the steam dischargechamber 90 and the lubrication chamber 102 can be maintained.

During a transition period prior to completion of warming-up, if thepressure of the lubrication chamber 102 becomes lower than the pressureof the steam discharge chamber 90, the steam in the steam dischargechamber 90 might be expected to flow into the lubrication chamber 102via the third breather passage B3, the second breather passage B2, thefirst breather passage B1, the upper breather chamber 103, and the lowerbreather chamber 101, but after the completion of warming-up, because ofthe leakage of steam into the lubrication chamber 102, the pressure ofthe lubrication chamber 102 becomes higher than the pressure of thesteam discharge chamber 90, and the above-mentioned oil and steamseparation is started.

In a Rankine cycle system in which steam (or water), which is theworking medium, circulates in a closed circuit, it is necessary to avoidas much as possible the oil from being mixed with the working medium andcontaminating the system; the mixing of the oil with the steam (orwater) can be minimized by the lower breather chamber 101 separating theoil and the upper breather chamber 103 separating the condensed water,thus reducing the load imposed on a filter separating the oil, achievinga reduction in size and a reduction in cost, and thereby preventingcontamination and degradation of the oil.

In the expander 113 employing oil as the lubricating medium for eachsliding section, even by taking the above-mentioned countermeasures asmall amount of water, which is the working medium, cannot be preventedfrom becoming mixed with the oil. Such water that has mixed with the oildegrades the lubrication performance, and it is necessary to separatethe water from the oil and return the water to the closed circuit of theRankine cycle system. On the other hand the oil, which is thelubricating medium, also cannot be prevented from becoming mixed withthe water, which is the working medium, in the expander 113. If thewater having the oil mixed therewith circulates around the closedcircuit of the Rankine cycle system, the oil affects the performance andthe durability of the evaporator and the condenser, and it is thereforenecessary to separate the oil from the water and return the oil to thelubricating system of the expander 113.

The overall arrangement of the Rankine cycle system that includes theexpander 113 is now explained with reference to FIG. 19.

Arranged in the working medium circulation circuit 110 of the Rankinecycle system are an evaporator 112 that generates high-temperature,high-pressure steam, which is a gas-phase working medium, by heatingwater, which is a liquid-phase working medium, using exhaust gas from aninternal combustion engine 111 as the source of heat; the expander 113that generates mechanical energy by the high-temperature, high-pressuresteam generated by the evaporator 112; a condenser 114 that cools thedecreased temperature, decreased pressure steam discharged from theexpander 113 so as to turn it back into water; and a feed pump 115 thatresupplies the water discharged from the condenser 114 to the evaporator112.

The oil passage 91 through which the oil of the expander 113 iscirculated by the oil pump 92 is provided with a radiator 116, aprefilter 117, and water separating means 118, and the water separatedby the water separating means 118 is returned to the working mediumcirculation circuit 110 of the Rankine cycle system via a water returnpassage 120 in which a one-way valve 119 is disposed. The oil from whichthe water has been separated by the water separating means 118 isreturned to the expander 113 via the oil passage 91 and the oil pump 92.

As shown in FIG. 20 to FIG. 22, the water separating means 118 isprovided with a coalescer type upstream side water separating device 121and a coalescer type downstream side water separating device 122 inline. The upstream side water separating device 121 is for separatingwater from an oil-water mixture in which the oil supplied from theexpander 113 is mixed with a small amount of water; a hydrophilicultrafine nylon fiber cylindrical filter element 124 is disposed withina casing 123, and the oil-water mixture is supplied into the interior ofthe filter element 124. The downstream side water separating device 122is for separating oil from a water-oil mixture in which the watersupplied from the upstream side water separating device 121 is mixedwith a small amount of oil; a hydrophilic ultrafine nylon fibercylindrical filter element 126 is disposed within a casing 125, and thewater-oil mixture is supplied into the interior of the filter element126. A water exit of the upstream side water separating device 121 isprovided with an upstream side switch valve 127, and a water exit of thedownstream side water separating device 122 is provided with adownstream side switch valve 128.

The upstream side switch valve 127 and the downstream side switch valve128 are normally closed; by supplying in this state from the expander113 the oil-water mixture in which the oil is mixed with a small amountof water, as is clear from FIGS. 23A and 23B, while the oil-watermixture passes from the inside to the outside through the filter element124 of the upstream side water separating device 121, the small amountof water contained in the oil is captured by the ultrafine nylon fiberand gradually increases its size, and when it turns into water dropletshaving a diameter of on the order of 2 to 3 mm, the water droplets alonefall downward due to the difference in specific gravity between waterand the oil, which is lighter than water, thus being separated from theoil, which goes upward. The oil from which water has been separated isreturned to the lubrication system of the expander 113 by the oil pump92 disposed in the oil passage 91.

In order to prevent the water that has been collected at the bottom ofthe casing 123 of the upstream side water separating device 121 frommixing again with the oil due to vibration, etc. accompanying travel ofan automobile equipped with the Rankine cycle system, a large number ofpartitions 123 a are provided on the bottom of the casing 123 so as tosuppress free flow of the water. Instead of these partitions 123 a, itis also possible to arrange a material having excellent waterabsorptivity such as a sponge on the bottom of the casing 123, and freeflow of water can be suppressed by absorbing the water with thematerial.

In this way, when the amount of water that has been collected at thebottom of the upstream side water separating device 121 increases,before the water mixes again with the oil that is to be returned to theexpander 113, the upstream side switch valve 127 is opened so as tosupply the water that has been collected at the bottom of the upstreamside water separating device 121 to the downstream side water separatingdevice 122. Since the water that has been collected at the bottom of theupstream side water separating device 121 still contains a small amountof oil, the oil is further separated in the downstream side waterseparating device 122. As is clear from FIGS. 24A and 24B, in thedownstream side water separating device 122, when the water-oil mixturepasses from the inside to the outside through the filter element 126,the small amount of oil contained in the water is captured by theultrafine nylon fiber and gradually increases its size, and when itturns into oil droplets having a diameter of on the order of 2 to 3 mm,the oil droplets alone float upward due to the difference in specificgravity between the water and the oil, which is lighter than the water,thus being separated from the water, which goes downward.

In order to prevent the oil that has been collected at the top of thecasing 125 of the downstream side water separating device 122 frommixing again with water due to vibration, etc. accompanying travel of anautomobile equipped with the Rankine cycle system, a large number ofpartitions 125 a are provided at the top of the casing 125 so as tosuppress free flow of the oil. Instead of these partitions 125 a, it isalso possible to arrange a sponge, etc., thus obtaining the sameeffects.

The oil that has been separated from the water-oil mixture in thedownstream side water separating device 122 is returned to thelubrication system of the expander 113 by means of the oil pump 92disposed in the oil passage 91. When a predetermined amount of waterfrom which the oil has been separated has been collected at the bottomof the downstream side water separating device 122, the downstream sideswitch valve 128 opens, and the water is returned to the working mediumcirculation circuit 110 of the Rankine cycle system via the water returnpassage 120 in which the one-way valve 119 is disposed. During thisprocess, by closing the downstream side switch valve 128 before thewater that has been collected at the bottom of the downstream side waterseparating device 122 is completely discharged, the oil can be preventedfrom flowing into the working medium circulation circuit 110 of theRankine cycle system.

Control of the opening and closing of the upstream side switch valve 127and the downstream side switch valve 128 can be carried out on the basisof the oil content of the water that is collected in, for example, theupstream side water separating device 121 and the downstream side waterseparating device 122. More specifically, since water is electricallyconductive and oil is electrically nonconductive, as the oil content ofthe water increases, the electrical resistance increases, and the oilcontent can be detected based on this.

The nylon fiber-made filter elements 124 and 126 of the upstream sidewater separating device 121 and the downstream side water separatingdevice 122 have a heat resistant temperature of about 80° C., whereasthe temperature of the oil residing in the oil pan 19 of the expander113 reaches about 120° C. Therefore, by reducing the temperature of theoil to the heat resistant temperature of the filter elements 124 and 126or lower by means of the radiator 116 provided on the upstream side ofthe water separating means 118, it is possible to ensure that theupstream side water separating device 121 and the downstream side waterseparating device 122 function, and increase the durability.

Moreover, since the working medium contained in the oil that has passedthrough the radiator 116 is cooled so as to become liquid-phase statewater, in comparison with a case in which the oil is separated from theworking medium in a state in which steam and water are mixed, the waterseparation performance of the water separating means 118 can beenhanced. Furthermore, by removing dust from the oil-water mixture bymeans of the prefilter 117 downstream of the radiator 116, clogging ofthe filter elements 124 and 126 of the upstream side water separatingdevice 121 and the downstream side water separating device 122 can beprevented, thereby increasing the durability. It is also possible forthe water separating means 118 to be mounted outside the expander 113and separately from the expander 113, or for it to be integrated withthe expander 113.

When the amount of steam supplied to the expander 113 changes accordingto the output state of the internal combustion engine 111 and,furthermore, if the internal combustion engine 111 has just started andwarm-up of the expander 113 has not been completed, since the amount ofsteam leaking past the clearance of each of the sliding sections alsoincreases, the mixing ratio of the oil-water mixture supplied from theexpander 113 to the water separating means 118 also varies. In thiscase, when an attempt is made to separate the water from the oil using asingle water separating device, there are the problems that since thecapacity of the water separating device is insufficient, the oil mightmix with the water thus separated, and if the capacity is increased, thedimensions of the water separating device will increase. However, as inthis embodiment, by arranging the upstream side water separating device121 and the downstream side water separating device 122, which havedifferent characteristics, in two stages, the water separationperformance can be improved while reducing the dimensions of the waterseparating means 118.

Since the upstream side switch valve 127 and the downstream side switchvalve 128 are normally closed, even when a large amount of oil-watermixture flows in from the expander 113 in a surge, the oil-containingwater can be prevented from flowing from the water separating means 118into the working medium circulation circuit 110 of the Rankine cyclesystem. Moreover, since the coalescer type water separating means 118,which carries out separation utilizing the difference in specificgravity between water and oil, has a smaller pressure loss than othermembrane type filters, the load on the oil pump 92 can be alleviated.

A method for separating the water from the oil of the expander 113 isexplained above, and a method for separating the oil from the watercirculating in the working medium circulation circuit 110 of the Rankinecycle system is now explained below.

As shown in FIG. 19, disposed in line between the expander 113 and thefeed pump 115 in the working medium circulation circuit 110, throughwhich water of the Rankine cycle system circulates, are a gas/liquidseparator 131, the condenser 114, water purifying means 132, and a tank133. Disposed in line in a bypass 134 branching from the gas/liquidseparator 131 and bypassing the condenser 114 are an oil pump 135 b forfeeding water-containing oil, a prefilter 136, oil separating means 137,and a filter 138.

The working medium discharged from the expander 113 is saturated steam(water-containing steam), and contains a trace amount of oil mixedtherewith in the expander 113 and a trace amount of abraded powder(sludge) generated in each of the sliding sections of the expander 113.The gas/liquid separator 131 separates gas-phase steam from thesaturated steam and supplies it to the condenser 114, and separatesliquid-phase water containing the oil or the sludge. In this way, byseparating only steam containing no oil and sludge and supplying it tothe condenser 114 by means of the gas/liquid separator 131, it ispossible to prevent water condensed within the condenser 114 from beingcooled excessively and the condensation performance of the condenser 114from being degraded due to contamination. In the condenser 114,degassing of non-condensed gas contained in the water is also carriedout at the same time. The water containing oil and sludge separated bythe gas/liquid separator 131 is supplied to the prefilter 136 by the oilpump 135 b of the bypass 134, and comparatively large-size sludgecontained in the water is removed in advance in order to preventclogging of the oil separating means 137 on the downstream side of theprefilter 136.

As shown in FIG. 25, the oil separating means 137 is for separating theoil contained in the water. The structure thereof is of a coalescertype, which is substantially the same as that of the downstream sidewater separating device 122 of the water separating means 118; ahydrophobic ultrafine nylon fiber cylindrical filter element 140 isdisposed within a casing 139, and a water-oil mixture in which a smallamount of the oil is mixed with the water is supplied to the interior ofthe filter element 140. In the oil separating means 137, when thewater-oil mixture passes through the filter element 140 from the insideto the outside, the small amount of oil contained in the water iscaptured by the ultrafine nylon fiber and gradually increases its size,and when it turns into oil droplets having a diameter of on the order of2 to 3 mm, the oil droplets alone float upward due to the difference inspecific gravity between the oil and water, which is lighter than oil,thus being separated from the water, which goes downward. In order toprevent the oil that has been collected at the top of the casing 139 ofthe oil separating means 137 from mixing again with the water due tovibration, etc. accompanying travel of an automobile equipped with theRankine cycle system, a large number of partitions 139 a are provided onthe top of the casing 139 so as to suppress free flow of the oil.Instead of these partitions 139 a, it is also possible to arrange asponge, etc., and the same effects can be obtained.

In this way, since liquid-phase water from which gaseous steam has beenremoved by the gas/liquid separator 131 is supplied to the oilseparating means 137, in comparison with a case in which oil isseparated in a state in which steam and water are mixed, the oilseparation performance of the oil separating means 137 can be enhanced.Moreover, since the water that has passed through the gas/liquidseparator 131 is cooled to 80° C. or lower, which is the heat resistanttemperature of the filter element 140 of the oil separating means 137,the oil separation performance and the durability of the oil separatingmeans 137 can be ensured. Furthermore, since the oil separating means137 is of the coalescer type, which carries out separation by utilizingthe difference in specific gravity between water and oil, pressure losscan be suppressed compared with a case in which other membrane typefilters are used, and the load on the oil pump 135 b can be alleviated.The oil that has been separated from the water by the oil separatingmeans 137 is returned to the oil passage 91 of the expander 113 via anoil return passage 142 in which a one-way valve 141 is disposed.

The water discharged from the oil separating means 137 into the bypass134 contains small-sized oil droplets (no greater than 1 μm) that couldnot be separated by the oil separating means 137, and these oil dropletsare adsorbed by a filter 138 employing active carbon as the filteringmaterial and removed. The water that has passed through the filter 138and the water that has returned from the expander 113 via the waterreturn passage 120 are supplied to the water purifying means 132. Thewater purifying means 132 includes a microfiltration (MF) membrane, anultrafiltration (UF) membrane, a reverse osmosis filtration (RO)membrane, etc., and microscopic sludge that could not be separated bythe prefilter 136 can be removed from the water. Furthermore, the waterpurifying means 132 carries out a water purification treatment employingion exchange, an alkalinization treatment, a dissolved oxygen removaltreatment, etc., thereby preventing contamination and corrosion of eachsection of the Rankine cycle system. The water that has passed throughthe water purifying means 132 is supplied to the feed pump 115 via thetank 133.

As hereinbefore described, since the water separating means 118 forseparating the working medium mixed with the oil for lubricating theexpander 113 is provided at a position where the working medium isliquid-phase state water, the water can be separated from the oil bymaking the water separating means 118 function effectively. Similarly,since the oil separating means 137 for separating the oil from theworking medium of the Rankine cycle system is provided at a positionwhere the working medium is liquid-phase state water, the oil can beseparated from the water by making the oil separating means 137 functioneffectively.

Furthermore, since the water that has been separated from the oil in thewater separating means 118 and the oil separating means 137 is returnedto the working medium circulation circuit 110, it is unnecessary toreplenish the working medium circulation circuit 110 with water, andsince the oil that has been separated from water is returned to theexpander 113, it is unnecessary to replenish the expander 113 with oil.

Although an embodiment of the present invention is explained above, thepresent invention can be modified in a variety of ways without departingfrom the spirit and scope thereof.

For example, in the embodiment, the internal combustion engine 111 isillustrated as the heat engine, but the present invention can also beapplied to a Rankine cycle system employing a heat engine other than theinternal combustion engine 111.

Furthermore, in the embodiment, the water separating means 118 comprisesthe upstream side water separating device 121 and the downstream sidewater separating device 122, but three or more water separating devicesmay be provided.

INDUSTRIAL APPLICABILITY

As hereinbefore described, the present invention can be appropriatelyapplied to a Rankine cycle system utilizing waste heat of an internalcombustion engine of an automobile, but it can also be applied to aRankine cycle system utilizing waste heat of an internal combustionengine other than one of an automobile, or a heat engine other than aninternal combustion engine.

1. A Rankine cycle system comprising a working medium circulationcircuit (110) through which a working medium is circulated and thatincludes an evaporator (112) that makes a working medium of ahigh-temperature, high-pressure gas-phase by heating the working mediumin a liquid-phase by means of waste heat of an internal combustionengine (111), an expander (113) in the circuit (110) that converts theheat and pressure of the working medium of a gas-phase supplied from theevaporator (112) into mechanical energy, a condenser (114) in thecircuit (110) that cools the gas-phase working medium whose temperatureand pressure have decreased in the expander (113) to turn the workingmedium back into the liquid-phase working medium, and a feed pump (115)in the circuit (110) that supplies the liquid-phase working mediumdischarged from the condenser (114) to the evaporator (112), alubricating medium circulating passage (91) through which a lubricatingmedium that is different from the working medium is circulated, whereinthe expander (113) has a sliding section thereof lubricated by thelubricating medium, the Rankine cycle system further comprising: workingmedium separating means (118) for separating from the lubricating mediumthe working medium that has become mixed with the lubricating medium inthe expander (113), and the working medium separating means (118) isprovided in the lubricating medium circulating passage (91) at aposition where the working medium is in a liquid-phase state, andlubricating medium separating means (137) for separating from theworking medium the lubricating medium that has become mixed with theworking medium in the expander (113), wherein the lubricating the mediumseparating means (137) is provided at a position on the downstream sideof the expander (113) where the working medium is in a liquid-phasestate.
 2. The Rankine cycle system according to claim 1, wherein theworking medium separating means (118) exhibits a function of separatingthe working medium in a predetermined temperature range, and the workingmedium separating means (118) is provided at a position where thelubricating medium is in the predetermined temperature range.
 3. TheRankine cycle system according to claim 1, wherein the working mediumseparating means (118) is formed by connecting at least two workingmedium separating devices (121, 122) in line.
 4. The Rankine cyclesystem according to claim 1, wherein the lubricating medium separatingmeans (137) exhibits a function of separating the lubricating medium ina predetermined temperature range, and the lubricating medium separatingmeans (137) is provided at a position where the liquid-phase workingmedium is in the predetermined temperature range.
 5. The Rankine cyclesystem according to claim 1, wherein it further comprises a gas/liquidseparator (131) for separating a liquid phase portion contained in theworking medium discharged from the expander (113) into the workingmedium circulation circuit (110), the liquid-phase working mediumseparated by the gas/liquid separator (131) being supplied to thelubricating medium separating means (137).
 6. The Rankine cycle systemaccording to claim 1, wherein it further comprises working mediumpurifying means (132) for removing cations or dissolved gas contained inthe working medium that has been discharged from the expander (113) intothe working medium circulation circuit (110) and that has been turnedback into the liquid phase state.
 7. The Rankine cycle system accordingto claim 1, wherein the lubricating medium from which the working mediumhas been separated by the working medium separating means (118) isreturned to the expander (113).
 8. The Rankine cycle system according toclaim 1, wherein the working medium separated from the lubricatingmedium by the working medium separating means (118) is returned to theworking medium circulation circuit (110).
 9. The Rankine cycle systemaccording to claim 1, wherein the working medium separating means (118)makes droplets of the working medium contained in the lubricating mediumbecome coarse, and the working medium is separated by virtue of adifference in specific gravity between the lubricating medium and theworking medium that has been made into coarse droplets.
 10. The Rankinecycle system according to claim 1, wherein the working medium separatingmeans (118) is of a coalescer type.
 11. The Rankine cycle systemaccording to claim 10, wherein the working medium separating means (118)comprises a filter element (124, 126) formed from hydrophobic fiber. 12.A Rankine cycle system comprising a working medium circulation circuit(110) through which a working medium is circulated and that includes anevaporator (112) that makes the working medium a high-temperature,high-pressure gas-phase working medium by heating the working medium ina liquid-phase by means of waste heat of an internal combustion engine(111) mounted on a vehicle, an expander (113) in the circuit (110) thatconverts the heat and pressure of the working medium of a gas-phasesupplied from the evaporator (112) into mechanical energy, a condenser(114) in the circuit (110) that cools the gas-phase working medium whosetemperature and pressure have decreased in the expander (113) in thecircuit (110) to turn the working medium back into the liquid-phaseworking medium, and a feed pump (115) that supplies the liquid-phaseworking medium discharged from the condenser (114) to the evaporator(112), a lubricating medium circulating passage (91) through which alubricating medium that is different from the working medium iscirculated, wherein the expander (113) has a sliding section thereoflubricated by a lubricating medium that is different from the workingmedium, the Rankine cycle system further comprising: working mediumseparating means (118) provided in the lubricating medium passage (91)at a position where the working medium is in a liquid state forseparating from the lubricating medium the working medium that hasbecome mixed with the lubricating medium, and the lubricating medium isa hydrophobic oil containing no extreme pressure additive having surfaceactivity for preventing emulsification of a mixture of the working andthe lubricating mediums, and lubricating medium separating means (137)for separating from the working medium the lubricating medium that hasbecome mixed with the working medium in the expander (113), wherein thelubricating medium separating means (137) is provided at a position onthe downstream side of the expander (113) where the working medium is ina liquid-phase state.
 13. The Rankine cycle system according to claim 1,wherein the working medium separating means (118) is provided with acoalescer upstream side water separating device (121) and a coalescerdownstream side water separating device (122) in line.
 14. The Rankinecycle system according to claim 13, wherein the upstream side waterseparating device (121) is for separating water from an oil-watermixture in which the oil supplied from the expander (113) is mixed witha small amount of water, the upstream side water separating device (121)including a hydrophobic ultrafine nylon fiber cylindrical filter element(124), and the oil-water mixture being supplied into an interior of thefilter element (124).
 15. The Rankine cycle system according to claim13, wherein the downstream side water separating device (122) is forseparating oil from a water-oil mixture in which the water supplied fromthe upstream side water separating device (121) is mixed with a smallamount of oil, the downstream side water separating device (122)including a hydrophobic ultrafine nylon fiber cylindrical filter element(126), and the water-oil mixture is supplied into an interior of thefilter element
 126. 16. The Rankine cycle system according to claim 13,further comprising a prefilter (117) the removing dust from theoil-water mixture downstream of a radiator (116), the prefilterpreventing clogging of filter elements (124) and (126) of the upstreamside water separating device (121) and the downstream side waterseparating device (122).
 17. The Rankine cycle system according to claim1, wherein an oil pump (135 b) for feeding water-containing oil, aprefilter (136), the lubricating medium separating means (137), and afilter (138) are disposed in line in a bypass (134) branching from agas/liquid separator (131) and bypassing the condenser (114).
 18. TheRankine cycle system according to claim 1, wherein the working mediumseparating means (118) and the lubricating medium separating means (137)are of a coalescer type, and the working medium separating means (118)makes droplets of the working medium contained in the lubricating mediumbecome coarse and the lubricating medium separating means (137) makesdroplets of the lubricating medium contained in the working mediumbecome coarse, so that the working medium at the working mediumseparating means (118) and the lubricating medium at the lubricatingmedium separating means (137) are each separated by virtue of adifference in specific gravity between the lubricating medium and theworking medium that has been made into the coarse droplets at respectiveseparating means (118, 137).
 19. The Rankine cycle system according toclaim 1, wherein the internal combustion engine (111) is mounted on avehicle.
 20. The Rankine cycle system according to claim 1, wherein theworking medium separating means (118) exhibits a function of separatingthe working medium in a predetermined temperature range, and the workingmedium separating means (118) is provided at a position where thelubricating medium is in the predetermined temperature range, whereasthe lubricating medium separating means (137) exhibits a function ofseparating the lubricating medium in a predetermined temperature range,and the lubricating medium separating means (137) is provided at aposition where the liquid-phase working medium is in the predeterminedtemperature range.